Mini Boss & Weapon power-up!

v0.1.5-Alpha build.8;
- Fixed bug where player dies but shield still draws.
- Fixed some enemies not spawning at the correct size.
- Cleaned up the way the player is drawn to the screen.
- Added ability to level up cannon and increase shots.
- Added big red mini-Boss.
- tweeked enemies speeds, and power-up chance.
- Started work on the background but got side tracked.